Method for improving acoustic noise attenuation in hand-free devices

Abstract

The present invention relates to a method for improving acoustic noise attenuation, in which the method includes an adaptive control for partial-band echo compensation as well as global-band post-filtering for suppressing residual echo in hand-free devices. This method also uses a level balance as well as controllable frequency-selective echo compensation with partial-band processing. After the frequency-selective echo compensation, the signal is submitted to a post-filtering in another frequency-selective filter using a Wiener-equation adjustment algorithm (Wiener filtering). A single control value (increment vector) is used for controlling both the frequency-selective echo compensation and the other filter. This method can thus be implemented with a very reduced amount of calculations so that it can also be used in simple consumer-directed processors.

What is claimed is:  
     
       1. A method for improving acoustic sidetone suppression in hands-free telephones, which comprises: 
       providing a hands-free telephone with a level discriminator and a Wiener filter defined by a frequency-selective filter having a Wiener setting algorithm;  
       subjecting an outgoing signal to a frequency-selective echo cancellation process utilizing subband processing;  
       after the echo cancellation process, post filtering the outgoing signal in the wiener filter; and  
       using a single controlled variable step-size vector {overscore (α)}(k) both to control the frequency-selective echo cancellation process and to control the Wiener filter.  
     
     
       2. The method according to  claim 1 , which comprises using, a plurality of different sampling rates. 
     
     
       3. The method according to  claim 2 , which comprises: 
       performing the echo-cancellation process with adaptive filters; and  
       providing the Wiener filter with adaptive filters.  
     
     
       4. The method according to  claim 1 , which comprises: 
       performing the echo-cancellation process with adaptive filters; and  
       providing the Wiener filter with adaptive filters.  
     
     
       5. The method according to  claim 1 , which comprises performing the echo-cancellation process with a filter bank in frequency subbands. 
     
     
       6. The method according to  claim 1 , which comprises using power-based estimates and correlation-based analyses to control both an adaptation and a step size. 
     
     
       7. The method according to  claim 1 , which comprises estimating power transmission factors in subbands in order to determine a step size. 
     
     
       8. The method according to  claim 1 , wherein: 
       the echo-cancellation process supplies an estimated value for a return loss introduced by the echo-cancellation process; and  
       the Wiener filter supplies an estimated value for a return loss introduced by the Wiener filter.  
     
     
       9. The method according to  claim 8 , which comprises using the estimated value from the echo-cancellation process and the estimated value from the Wiener filter to control an attenuation of the level discriminator. 
     
     
       10. The method according to  claim 1 , which comprises simultaneously detecting activity of both participants in a call. 
     
     
       11. The method according to  claim 10 , which comprises, in duplex communication, reducing an overall attenuation of the level discriminator.